(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Text Book Of Mechanical Engineering"

658

Trip Gears.

large portion cut away, and are rotated by spindles to which they
are connected loosely.    The steam pipe is shewn at , and // are
the exhaust pipes, forming the cylinder supports.     Taking the
valve gear, A is the eccentric rod,' which by a to-and-fro motion
rotates the disc or wrist-plate B ; to the latter are connected the
four valve rods, two of them at cc actuating the exhaust valves,
the other two at D D working the steam valves.    The exhaust rod
CE is directly connected to the valve lever EF, and moves it
through rather less tban 90.    The steam-valve rod DG is more
complicated, consisting of two parts: one, DORP, attached to the
wrist plate;  the other, QNG, connected to the valve lever GJ.
These tend to separate, by reason of the force in the compressed
spring T, but are prevented by "the spring catches PP.    If, how-
ever, the latter are prised apart, spring T is released, and, pulling
j rapidly to the left, closes the steam valve.    The prising action
is obtained by the toe lever MN, which, pinned to QNG at N, rocks
on ftiferum M.   As the pin D moves from z to D, the rod D G takes
a more crosswise position relatively to the toe N, and at some
intermediate position the catches PP liberate the parts r> and o,
permitting the valve to be closed.    When D moves back to z, p p
regain their normal condition and D and G are connected.    The
position of fulcrum M determines where, between z and D, the toe
shall release part G, and this is decided by the height of governor
sleeve, the latter being connected to rod ;;/.    When the governors
rise, ;// is pulled to the left, moving M an equal amount to the
right, levers WK and WL being geared together at x.    This causes
the toe to separate PP at an earlier part of the stroke z to D, and
the converse will happen when the governors fall.    Lastly, the
dash-pot s being full of air only capable of passing out at u,
reduces the shock caused by the sudden release of the spring T,
the set screws serving to regulate the air passage, and the back
chamber v is usually connected to the condenser to ensure decision.
The Proell Valve Gear is another good trip gear.    The
lever D E, Crocking op fulcrum E, may for the present be looked
upon as rigidly contacted to the arm F F, and toes F G.    At point
E is attachejl the eccentric rod, and/a movement of D to the right
will cause the left-hand toe G, trailing along HJ, to finally slip,
when spring L closes the steam valve B.    Meantime, the right-